1. Field of the Invention
Subject matter of the invention is a system for determining the properties of tissue parts of a living organism, a device for attaching an optoelectronic measuring device to the surface of the tissue, and a method for the non-invasive determination of the properties of tissue parts.
To date, the majority of determinations of properties of living organisms is carried out in the form of invasive methods. The structure of tissue is characterized, for example, with the aid of surgical methods. When an analyte is to be determined in body fluids, a certain amount of body fluid was obtained from the tissue, i.e. the human body, by obtaining blood from the veins, for example. These invasive methods lead to tissue damage, particularly when several determinations are carried out successively. It is for this reason that methods have then developed recently where the properties of tissue of the living organism can be determined even without withdrawing body fluids or surgical intervention.
2. Description of the Related Art
WO 94/10901 describes a method and device for analyzing glucose in a biological matrix which utilizes the multiple scattering of light by tissue. This patent application discloses that a measuring head is attached to a suitable site of the body weight the aid of an adhesive tape. In order to keep away foreign light sources, the measuring head is provided with a skin contact part whose diameter is considerably larger than the one of the measuring opening used. The ring is made of a non-transparent material and tightly urges against the skin.
U.S. Pat. No. 5,226,417 describes a device where a light beam is sent through a finger. The device is equipped with light-emitting diodes and photodetectors that are flexibly connected to one another so as to be arranged on opposite sides of the finger. The device also has wings to shield off light from the environment when the device is attached to the finger.
Moreover, the device described is provided with an adhesive tape to attach the light source and the photodetector to the skin. Object of the adhesive is to increase the resistance against undesired removal of the device.
U.S. Pat. No. 4,928,691 also describes a flexible device which comprises a photosensor and a light source. These elements are mounted on to a flexible material which, in turn, can be attached to various sites on the body. This is accomplished with the aid of an adhesive strip.
U.S. Pat. No. 5,267,563 describes a pulsoximeter whose sensors are attached to the skin with the aid of an adhesive plaster. The plaster contains substances to stimulate the blood flow. Once the drug has entered the skin, a measurement is carried out. When the measurement is completed the instrument is removed from the skin.
EP-A-0 573 137 describes a pulsoximeter where the sensors are attached to the skin with the aid of an adhesive strip which contains substances that stimulate the blood flow. In order to shield off light from the environment, the photodetector has a wall that reaches through the adhesive strip on to the skin. This device was designed for disposable use as are the other above mentioned devices.
U.S. Pat. No. 4,685,464 describes an element for attaching a sensor for the non-invasive measurement of blood components. The sensor can be attached to a finger.
EP-A-0 572 684 describes a sensor for monitoring life signs, especially saturation with oxygen. Said sensor can be attached to various sites of the skin. To do this, the described system has transmitter element as well as a receiver element which have been designed for multiple use. Moreover, the system has a housing to contain the above listed elements and connections for attachment of the above-mentioned elements.
In the devices and methods described in the above mentioned prior art, accuracy of positioning is irrelevant as a pulsoximetry application depends on the pulse signal rather than the site of the application.
U.S. Pat. No. 4,798,955 describes means for use of a non-invasive measuring device for several subject. It describes a flexible band which is placed around the upper arm of the subjects. The band has an element for individually adjusting the position of the band and, hence, of a measuring window. Experience has shown, however, that the reproducibility of the individual measurements is not satisfactory.